I want to test my function that takes a string, a returns all the pairs of characters as an array s.t.
func pairsOfChars(_ s: String) -> [(Character,Character)] {
let strArray = Array(s)
var outputArray = [(Character,Character)]()
for i in 0..<strArray.count - 1 {
for j in i + 1..<strArray.count {
outputArray.append( (strArray[i], strArray[j]) )
}
}
return outputArray
}
So I want to create a suite of tests using XCTestCase. I usually use XCTestCase and XCTAssertEqual but these are only appropriate for C scalar types. This means that the following test case returns an error:
class pairsTests: XCTestCase {
func testNaive() {
measure {
XCTAssertEqual( pairsOfChars("abc") , [(Character("a"),Character("b")),(Character("a"),Character("c")),(Character("b"),Character("c")) ] )
}
}
}
I could convert to a string, but I'm thinking there is a better solution.
How can I test an output of an array of pairs of characters [(Character,Character)]
Your notion of a nonscalar is a total red herring. The problem is one of equatability.
How can I test an output of an array of pairs of characters [(Character,Character)]
You can't, because there is no default notion of what it would mean to equate two such arrays. This is the old "tuples of Equatable are not Equatable" problem (https://bugs.swift.org/browse/SR-1222) which still rears its head with arrays. The == operator works on tuples by a kind of magic, but they are still not formally Equatable.
You could define equatability of arrays of character pairs yourself:
typealias CharPair = (Character,Character)
func ==(lhs:[CharPair], rhs:[CharPair]) -> Bool {
if lhs.count != rhs.count {
return false
}
let zipped = zip(lhs,rhs)
return zipped.allSatisfy{$0 == $1}
}
Alternatively, have your pairsOfChars return something that is more easily made equatable, such as an array of a struct for which Equatable is defined.
For example:
struct CharacterPair : Equatable {
let c1:Character
let c2:Character
// in Swift 4.2 this next bit is not needed
static func ==(lhs:CharacterPair, rhs:CharacterPair) -> Bool {
return lhs.c1 == rhs.c1 && lhs.c2 == rhs.c2
}
}
func pairsOfChars(_ s: String) -> [CharacterPair] {
let strArray = Array(s)
var outputArray = [CharacterPair]()
for i in 0..<strArray.count - 1 {
for j in i + 1..<strArray.count {
outputArray.append(CharacterPair(c1:strArray[i],c2:strArray[j]))
}
}
return outputArray
}
You would then rewrite the test to match:
XCTAssertEqual(
pairsOfChars("abc"),
[CharacterPair(c1:Character("a"),c2:Character("b")),
CharacterPair(c1:Character("a"),c2:Character("c")),
CharacterPair(c1:Character("b"),c2:Character("c"))]
)
Given the following array:
let ignoredViewControllerTypes:[UIViewController.Type] = [
ViewControllerB.self,
ViewControllerC.self
]
let allViewControllers = [
viewControllerAInstance,
viewControllerBInstance,
viewControllerCInstance,
viewControllerDInstance
]
What is the syntax to filter allViewControllers so that it excludes those types in ignoredViewControllerTypes?
I have tried this, but it doesn't work:
let filteredControllers = allViewControllers.filter{ !ignoredViewControllerTypes.contains($0.self) }
So what am I missing?
This should work:
let filteredControllers = allViewControllers.filter { viewController in
!ignoredViewControllerTypes.contains(where: { type(of: viewController) == $0 })
}
Let's break it down in subtasks:
you want to check if a controller should be allowed or not
func isAllowed(_ controller: UIViewController) -> Bool {
return !ignoredViewControllerTypes.contains { controller.isKind(of: $0) }
}
you want to filter an array of controllers:
let filteredControllers = allViewControllers.filter(isAllowed)
Note that isAllowed also filters subclasses of the ignored controllers, if you want exact type match then you should use #dan's answer.
As a bonus, and because I like functional programming, you can make isAllowed a pure and flexible function by converting it to a high-order function:
func doesntBelong(to prohibitedClasses: [AnyClass]) -> (AnyObject) -> Bool {
return { obj in
prohibitedClasses.contains { obj.isKind(of: $0) }
}
}
, which can be used like this:
let filteredControllers = allViewControllers.filter(doesntBelong(to: ignoredViewControllerTypes))
In Swift, how can I check if an element exists in an array? Xcode does not have any suggestions for contain, include, or has, and a quick search through the book turned up nothing. Any idea how to check for this? I know that there is a method find that returns the index number, but is there a method that returns a boolean like ruby's #include??
Example of what I need:
var elements = [1,2,3,4,5]
if elements.contains(5) {
//do something
}
Swift 2, 3, 4, 5:
let elements = [1, 2, 3, 4, 5]
if elements.contains(5) {
print("yes")
}
contains() is a protocol extension method of SequenceType (for sequences of Equatable elements) and not a global method as in
earlier releases.
Remarks:
This contains() method requires that the sequence elements
adopt the Equatable protocol, compare e.g. Andrews's answer.
If the sequence elements are instances of a NSObject subclass
then you have to override isEqual:, see NSObject subclass in Swift: hash vs hashValue, isEqual vs ==.
There is another – more general – contains() method which does not require the elements to be equatable and takes a predicate as an
argument, see e.g. Shorthand to test if an object exists in an array for Swift?.
Swift older versions:
let elements = [1,2,3,4,5]
if contains(elements, 5) {
println("yes")
}
For those who came here looking for a find and remove an object from an array:
Swift 1
if let index = find(itemList, item) {
itemList.removeAtIndex(index)
}
Swift 2
if let index = itemList.indexOf(item) {
itemList.removeAtIndex(index)
}
Swift 3, 4
if let index = itemList.index(of: item) {
itemList.remove(at: index)
}
Swift 5.2
if let index = itemList.firstIndex(of: item) {
itemList.remove(at: index)
}
Updated for Swift 2+
Note that as of Swift 3 (or even 2), the extension below is no longer necessary as the global contains function has been made into a pair of extension method on Array, which allow you to do either of:
let a = [ 1, 2, 3, 4 ]
a.contains(2) // => true, only usable if Element : Equatable
a.contains { $0 < 1 } // => false
Historical Answer for Swift 1:
Use this extension: (updated to Swift 5.2)
extension Array {
func contains<T>(obj: T) -> Bool where T: Equatable {
return !self.filter({$0 as? T == obj}).isEmpty
}
}
Use as:
array.contains(1)
If you are checking if an instance of a custom class or struct is contained in an array, you'll need to implement the Equatable protocol before you can use .contains(myObject).
For example:
struct Cup: Equatable {
let filled:Bool
}
static func ==(lhs:Cup, rhs:Cup) -> Bool { // Implement Equatable
return lhs.filled == rhs.filled
}
then you can do:
cupArray.contains(myCup)
Tip: The == override should be at the global level, not within your class/struct
I used filter.
let results = elements.filter { el in el == 5 }
if results.count > 0 {
// any matching items are in results
} else {
// not found
}
If you want, you can compress that to
if elements.filter({ el in el == 5 }).count > 0 {
}
Hope that helps.
Update for Swift 2
Hurray for default implementations!
if elements.contains(5) {
// any matching items are in results
} else {
// not found
}
(Swift 3)
Check if an element exists in an array (fulfilling some criteria), and if so, proceed working with the first such element
If the intent is:
To check whether an element exist in an array (/fulfils some boolean criteria, not necessarily equality testing),
And if so, proceed and work with the first such element,
Then an alternative to contains(_:) as blueprinted Sequence is to first(where:) of Sequence:
let elements = [1, 2, 3, 4, 5]
if let firstSuchElement = elements.first(where: { $0 == 4 }) {
print(firstSuchElement) // 4
// ...
}
In this contrived example, its usage might seem silly, but it's very useful if querying arrays of non-fundamental element types for existence of any elements fulfilling some condition. E.g.
struct Person {
let age: Int
let name: String
init(_ age: Int, _ name: String) {
self.age = age
self.name = name
}
}
let persons = [Person(17, "Fred"), Person(16, "Susan"),
Person(19, "Hannah"), Person(18, "Sarah"),
Person(23, "Sam"), Person(18, "Jane")]
if let eligableDriver = persons.first(where: { $0.age >= 18 }) {
print("\(eligableDriver.name) can possibly drive the rental car in Sweden.")
// ...
} // Hannah can possibly drive the rental car in Sweden.
let daniel = Person(18, "Daniel")
if let sameAgeAsDaniel = persons.first(where: { $0.age == daniel.age }) {
print("\(sameAgeAsDaniel.name) is the same age as \(daniel.name).")
// ...
} // Sarah is the same age as Daniel.
Any chained operations using .filter { ... some condition }.first can favourably be replaced with first(where:). The latter shows intent better, and have performance advantages over possible non-lazy appliances of .filter, as these will pass the full array prior to extracting the (possible) first element passing the filter.
Check if an element exists in an array (fulfilling some criteria), and if so, remove the first such element
A comment below queries:
How can I remove the firstSuchElement from the array?
A similar use case to the one above is to remove the first element that fulfils a given predicate. To do so, the index(where:) method of Collection (which is readily available to array collection) may be used to find the index of the first element fulfilling the predicate, whereafter the index can be used with the remove(at:) method of Array to (possible; given that it exists) remove that element.
var elements = ["a", "b", "c", "d", "e", "a", "b", "c"]
if let indexOfFirstSuchElement = elements.index(where: { $0 == "c" }) {
elements.remove(at: indexOfFirstSuchElement)
print(elements) // ["a", "b", "d", "e", "a", "b", "c"]
}
Or, if you'd like to remove the element from the array and work with, apply Optional:s map(_:) method to conditionally (for .some(...) return from index(where:)) use the result from index(where:) to remove and capture the removed element from the array (within an optional binding clause).
var elements = ["a", "b", "c", "d", "e", "a", "b", "c"]
if let firstSuchElement = elements.index(where: { $0 == "c" })
.map({ elements.remove(at: $0) }) {
// if we enter here, the first such element have now been
// remove from the array
print(elements) // ["a", "b", "d", "e", "a", "b", "c"]
// and we may work with it
print(firstSuchElement) // c
}
Note that in the contrived example above the array members are simple value types (String instances), so using a predicate to find a given member is somewhat over-kill, as we might simply test for equality using the simpler index(of:) method as shown in #DogCoffee's answer. If applying the find-and-remove approach above to the Person example, however, using index(where:) with a predicate is appropriate (since we no longer test for equality but for fulfilling a supplied predicate).
An array that contains a property that equals to
yourArray.contains(where: {$0.propertyToCheck == value })
Returns boolean.
The simplest way to accomplish this is to use filter on the array.
let result = elements.filter { $0==5 }
result will have the found element if it exists and will be empty if the element does not exist. So simply checking if result is empty will tell you whether the element exists in the array. I would use the following:
if result.isEmpty {
// element does not exist in array
} else {
// element exists
}
Swift 4/5
Another way to achieve this is with the filter function
var elements = [1,2,3,4,5]
if let object = elements.filter({ $0 == 5 }).first {
print("found")
} else {
print("not found")
}
As of Swift 2.1 NSArrays have containsObjectthat can be used like so:
if myArray.containsObject(objectImCheckingFor){
//myArray has the objectImCheckingFor
}
Array
let elements = [1, 2, 3, 4, 5, 5]
Check elements presence
elements.contains(5) // true
Get elements index
elements.firstIndex(of: 5) // 4
elements.firstIndex(of: 10) // nil
Get element count
let results = elements.filter { element in element == 5 }
results.count // 2
Just in case anybody is trying to find if an indexPath is among the selected ones (like in a UICollectionView or UITableView cellForItemAtIndexPath functions):
var isSelectedItem = false
if let selectedIndexPaths = collectionView.indexPathsForSelectedItems() as? [NSIndexPath]{
if contains(selectedIndexPaths, indexPath) {
isSelectedItem = true
}
}
if user find particular array elements then use below code same as integer value.
var arrelemnts = ["sachin", "test", "test1", "test3"]
if arrelemnts.contains("test"){
print("found") }else{
print("not found") }
Here is my little extension I just wrote to check if my delegate array contains a delegate object or not (Swift 2). :) It Also works with value types like a charm.
extension Array
{
func containsObject(object: Any) -> Bool
{
if let anObject: AnyObject = object as? AnyObject
{
for obj in self
{
if let anObj: AnyObject = obj as? AnyObject
{
if anObj === anObject { return true }
}
}
}
return false
}
}
If you have an idea how to optimize this code, than just let me know.
Swift
If you are not using object then you can user this code for contains.
let elements = [ 10, 20, 30, 40, 50]
if elements.contains(50) {
print("true")
}
If you are using NSObject Class in swift. This variables is according to my requirement. you can modify for your requirement.
var cliectScreenList = [ATModelLeadInfo]()
var cliectScreenSelectedObject: ATModelLeadInfo!
This is for a same data type.
{ $0.user_id == cliectScreenSelectedObject.user_id }
If you want to AnyObject type.
{ "\($0.user_id)" == "\(cliectScreenSelectedObject.user_id)" }
Full condition
if cliectScreenSelected.contains( { $0.user_id == cliectScreenSelectedObject.user_id } ) == false {
cliectScreenSelected.append(cliectScreenSelectedObject)
print("Object Added")
} else {
print("Object already exists")
}
what about using a hash table for the job, like this?
first, creating a "hash map" generic function, extending the Sequence protocol.
extension Sequence where Element: Hashable {
func hashMap() -> [Element: Int] {
var dict: [Element: Int] = [:]
for (i, value) in self.enumerated() {
dict[value] = i
}
return dict
}
}
This extension will work as long as the items in the array conform to Hashable, like integers or strings, here is the usage...
let numbers = Array(0...50)
let hashMappedNumbers = numbers.hashMap()
let numToDetect = 35
let indexOfnumToDetect = hashMappedNumbers[numToDetect] // returns the index of the item and if all the elements in the array are different, it will work to get the index of the object!
print(indexOfnumToDetect) // prints 35
But for now, let's just focus in check if the element is in the array.
let numExists = indexOfnumToDetect != nil // if the key does not exist
means the number is not contained in the collection.
print(numExists) // prints true
Swift 4.2 +
You can easily verify your instance is an array or not by the following function.
func verifyIsObjectOfAnArray<T>(_ object: T) -> Bool {
if let _ = object as? [T] {
return true
}
return false
}
Even you can access it as follows. You will receive nil if the object wouldn't be an array.
func verifyIsObjectOfAnArray<T>(_ object: T) -> [T]? {
if let array = object as? [T] {
return array
}
return nil
}
You can add an extension for Array as such:
extension Array {
func contains<T>(_ object: T) -> Bool where T: Equatable {
!self.filter {$0 as? T == object }.isEmpty
}
}
This can be used as:
if myArray.contains(myItem) {
// code here
}
I'm writing a test:
func test_arrayFromShufflingArray() {
var videos = [MockObjects.mockVMVideo_1(), MockObjects.mockVMVideo_2(), MockObjects.mockVMVideo_3()]
let tuple = ShuffleHelper.arrayFromShufflingArray(videos, currentIndex:1)
var shuffledVideos = tuple.0
let shuffleIndexMap = tuple.1
// -- test order is different
XCTAssert(videos != shuffledVideos, "test_arrayFromShufflingArray fail")
}
But on the last line I get the last line:
Binary operator '!=' cannot be applied to two '[VMVideo!]' operands
Arrays can be compared with == if the element type is Equatable:
/// Returns true if these arrays contain the same elements.
public func ==<Element : Equatable>(lhs: [Element], rhs: [Element]) -> Bool
But neither ImplicitlyUnwrappedOptional<Wrapped> nor Optional<Wrapped> conform to Equatable, even if the
underlying type Wrapped does.
Possible options are (assuming that VMVideo conforms to Equatable):
Change your code so that videos and shuffledVideos are
[VMVideo] arrays instead of [VMVideo!].
Compare the arrays elementwise:
XCTAssert(videos.count == shuffledVideos.count
&& !zip(videos, shuffledVideos).contains {$0 != $1 })
Define a == operator for arrays of implicitly unwrapped equatable
elements:
func ==<Element : Equatable> (lhs: [Element!], rhs: [Element!]) -> Bool {
return lhs.count == rhs.count && !zip(lhs, rhs).contains {$0 != $1 }
}
Swift can't tell how to compare two arrays to see if their contents are identical unless it knows how to compare individual elements. So you need to implement the == function on your class and adopt Equatable:
extension VMVideo: Equatable {
// nothing goes here, == function has to be at global scope
}
func ==(lhs: VMVideo, rhs: VMVideo) -> Bool {
// Up to you to determine what equality means for your object, e.g.:
return lhs.essentialProperty1 == rhs.essentialProperty1 &&
lhs.essentialProperty2 == rhs.essentialProperty2
}
EDIT To clarify how it interacts with NSObject and to troubleshoot your environment, please confirm the following:
class UnderstandsEqual: NSObject {}
let ok1: [UnderstandsEqual] = [UnderstandsEqual(), UnderstandsEqual()]
let ok2: [UnderstandsEqual] = [UnderstandsEqual(), UnderstandsEqual()]
ok1 == ok2 // no problem, evaluates to true
class DoesntUnderstand {}
let bad1: [DoesntUnderstand] = [DoesntUnderstand(), DoesntUnderstand()]
let bad2: [DoesntUnderstand] = [DoesntUnderstand(), DoesntUnderstand()]
bad1 == bad2 // produces a compile-time error
Martin R's answer was the better answer, but for this specific purpose I just converted to NSArray's and was able to use the == operator in Swift:
func test_arrayFromShufflingArray() {
let videos = [MockObjects.mockVMVideo_1(), MockObjects.mockVMVideo_2(), MockObjects.mockVMVideo_3()]
let videosNSArray: NSArray = videos.map { $0 }
let tuple = ShuffleHelper.arrayFromShufflingArray(videos, currentIndex:1)
let shuffledVideos = tuple.0
let shuffledVideosNSArray: NSArray = shuffledVideos.map { $0 }
// -- test order is different
XCTAssert(videosNSArray != shuffledVideosNSArray, "test_arrayFromShufflingArray fail")
// -- test elements are the same
let set = NSSet(array: videos)
let shuffledSet = NSSet(array: shuffledVideos)
XCTAssert(set == shuffledSet, "test_arrayFromShufflingArray fail")
}
I am using Swift 1.2 in Xcode 6.3.1
Following is my Person struct
struct Person {
let age: Int
init?(age: Int) { //Failable init
if age > 100 { return nil }
self.age = age
}
}
I am having a list of ages against which I have to make Person Objects.
I have made playground file.
let arr = Array(1...150) //Sample set of ages against which Person is created
var personList: [Person]!
and
personList = arr.map({ (val: Int) -> Person? in
return Person(age: val) //Makes object of type Person?
}).filter {
$0 != nil
}.map {
return $0!
}
Here I have uses map - filter - map because the first map invokes failable intializer, (hence it returns Person?) and personList is of type [Person].
Hence second function filters all the non nil objects and third map forcefully opens to optional therby making Person? to Person.
Is there a more easy/readable way out ? Chaining map-filter-map definitely seems to be an overkill for this
You can use flatMap to get rid of any nils in the array, this tutorial discusses the method in length, but the following will work best:
let personList = arr.flatMap { Person(age: $0) }
Note: This answer was given for Swift 1.2, the current
version at the time the question was posted. Since Swift 2 there is a better solution, see #Jeremie's answer.
I don't know of a built-in function that combines filter()
and map(). You can write the code slightly more compact using
the shorthand argument $0 in all closures:
let personList = arr.map { Person(age: $0) }
.filter { $0 != nil }
.map { $0! }
Of course you can define your own extension method which maps the
array elements and keeps only the non-nil results:
extension Array {
func optmap<U>(transform: T -> U?) -> [U] {
var result : [U] = []
for elem in self {
if let mapped = transform(elem) {
result.append(mapped)
}
}
return result
}
}
and then use it as
let personList = arr.optmap { Person(age: $0) }
You can use compactMap which is better that flatMap in this case to remove any nils in the array:
let personList = arr.compactMap { Person(age: $0) }
The Swift document declared:
Returns an array containing the non-nil results of calling the given
transformation with each element of this sequence.